Many micro-devices require optical access. Some micro-devices, such as digital micromirrors, need optical access in order to function, since light must be able to interact with the active elements of these micro-devices in order to achieve the desired results. By way of example, light must be able to enter and leave a digital micromirror device (“DMD”) in order to be reflected by the micromirror elements for image projection. For other micro-devices, optical access may be needed for inspection purposes. Regardless of the reason, there is a need for optical access in many micro-devices.
On the other hand, the active elements of such micro-devices may be fairly fragile, needing protection from environmental contamination in order to operate effectively and reliably. Due to the extremely small size of the active elements within micro-devices, even dust particles may interfere with proper functioning. Thus, there is a need to shield the active elements of micro-devices from any contamination or environmental factors that might detrimentally impact their operation.
The active elements of micro-devices are often housed within a package that is hermetically sealed, but which provides a transparent window in the cover allowing optical access. The window can allow for visual inspection of the active elements within the micro-device, and can also be configured to allow visual light or any other specific range of electromagnetic wavelengths to enter into and/or leave the micro-device. So in many digital micro-devices, such as DMDs, windows serve a crucial role by allowing the transfer of light for the operation of the device, while sheltering the active elements of the micro-device from environmental contaminants that might hinder performance.
FIG. 1 provides an example of a typical optical MEMS window, which to date have been constructed one at a time. Such optical MEMS windows affix glass within a metal frame. Typically, the metal frame is formed having an aperture for the transparent window and a lip or flange surrounding the aperture that can serve as a location for anchoring the window upon a package. Glass is then fused to the metal frame in order to form the overall window structure. The heat involved in this fusing process tends to ruin the surface finish of the glass, however, requiring grinding and/or polishing of both sides of the glass to provide a useful window. Then, the transparent window is typically treated with anti-reflective coatings. The entire window is then mounted to the package for the micro-device. Typically the metal frame for the optical MEMS window is welded in place in order to hermetically seal the active elements of the micro-device within the package beneath the window.
While these traditional optical MEMS windows function quite well, they are fairly costly to produce, requiring multiple steps to manufacture each separate window. Since each of the process steps, which tend to be relatively time and labor intensive, is performed for each individual window, the cost of each window is driven up. The high cost of production for these traditional windows adds to the overall cost of each MEMS device. Accordingly, there is a need for a production process for windows that would reduce their costs.